The present invention relates to a tracheal tube with an inflatable balloon, around the tube, the so called cuff which is in contact with the tracheal wall with the purpose of sealing the airway, and which is through a separate channel connected to the outside in order to monitor and regulate the pressure within the cuff. Such tracheal tubes are used for controlled ventilation of the lungs during anaesthesia and intensive care, during which he cuff seals up for respiratory air between the inside of the trachea and the tracheal tube. Apart from this, the cuff shall prevent liquid and secretions from entering the lungs. Additionally, it is important that the pressure of the cuff against the tracheal wall does not impede the blood supply to the tracheal mucosa. The best way to accomplish these functions is to use cuffs with a diameter larger than that of the trachea, because a homogeneous pressure on the tracheal wall is then achieved, as this pressure is regulated by the inside pressure in the cuff only. However, a high-volume cuff has certain drawbacks. The larger diameter of the cuff in relation to that of the trachea implies that the cuff has longitudinal folds when it is inflated inside the trachea, and these folds will create channels through which liquid and secretions with bacteria may get past the cuff and result in infection of the lungs.
From WO 95/09665 is known a tracheal tube comprising a cuff with a number of axially arranged ring-formed bulges providing a number of ring-formed contacts between the cuff and the trachea. From DE-A-35 19 626 (D2) is known a balloon catheter for the treatment of vessels, e.g. coronary vessels. The balloon is equipped with a distal portion comprising circumferential rings to help inflating the balloon.
The purpose of this invention is to design a tracheal tube which has the advantages of the known tracheal tubes, but prevents the disadvantage of forming channels between the trachea and the cuff. In accordance with the invention, this problem is solved with a tracheal tube as defined in claim 1.
More specifically, it is stated in claim 1 that the cuff has a number of local bulges distributed along the circumference of the balloon. In this way it is ensured that the channels, which are formed by the length-wise folds when the cuff is inflated inside the trachea, will be interrupted by areas with bulges. The thickness of the membrane in the bulges is reduced in comparison with the thickness of the membrane in the rest of the cuff. By this is ensured that the lengthwise folds which are formed, will be tightly closed by areas with bulges and that transport of liquid and secretions past the areas with local bulges is prevented.
By imparting to the bulges an elongate shape, as stated in claim 2, with the longitudinal axis in the direction of the circumference, it is furthermore ensured that the length-wise folds are interrupted by transverse bulges.
In another version according to claim 3, the bulges have an elongate shape with the longitudinal axis in an angled direction in relation to that of the circumference. As a result, the bulges become longer in the longitudinal direction, and transport of liquid in a length-wise fold is reduced, because a length-wise fold will pass a longer distance with thin-walled bulges, if the orientation of the bulges is angled compared to transversal.
By giving the balloon two or more rows of bulges, according to claim 4, the length-wise folds will be interrupted by one or more bulges, and the transport of liquid will be reduced.
It will be advantageous, as stated in claim 5, if the bulges in each row are staggered in relation to each other, so that any fold in the length-wise direction will be crossing a bulge.
In an advantageous version, according to claim 6, the bulges in two adjacent rows are placed with different angled directions of the longitudinal axis. By this, additional safety is obtained against uninterrupted folds with channels from the area above the cuff to the area below the cuff. As a result, any transport of liquid in a length-wise fold is reduced.
The channels that are formed when the bulges collapse against the inside of the tracheal wall must be very narrow in order to effectively prevent transport of fluid. Accordingly, the material of the bulges must be very soft and very thin-walled, and it has been proved that a good result is obtained with a wall-thickness of less than 30 micrometer. Because the areas with bulges are pressed against the tracheal wall, the reduced wall-thickness in the bulges will not reduce the ability of the cuff to resist pressure during the inflation.